| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 99 === The OFDM system has been a widely adopted technique for both wired and wireless transmission. It is well-known that one of the most important problem for the OFDM systems is the carrier frequency mismatch between the transmitter and the receiver. The frequency mismatch is called as carrier frequency o set (CFO). The CFO would destroy the subcarrier orthogonality of OFDM systems. As a result the performance of OFDM systems will degrade severely if CFO is not properly compensated. Therefore, It is important to precisely estimate and compensate CFO for OFDM systems.
In this thesis, the effect of CFO in OFDM systems is presented first, and then estimations and compensations of CFO are considered. We propose a simple modification for existing CFO estimation methods. It is a semi-blind method since we need to know the position of data subcarriers. The proposed method is simple but offer significant performance gain. In simulation results, we show that the performance is improved by using the proposed modification.
We also propose another semi-blind method which is low-complexity since it does not need any SVD or EVD operations. It is shown by simulation results that the performance of the proposed low-complexity method is the same as the existing method which needs SVD operation. Our methods do not take any training sequences or pilots, so we can improve the bandwidth efficiency.
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